fix: optimize serve/sourcemap startup from >180s to ~8s

Root cause: notify-debouncer-full with macos_kqueue caused 25K+
directory watch registrations to take >170s on large projects.

Changes:
- Replace notify-debouncer-full with notify-debouncer-mini to avoid
  FSEvents Create+Remove event cancellation and heavy per-watch overhead
- Remove macos_kqueue feature; use FSEvents (matches upstream Rojo)
- Fix VFS read guard: watch_enabled && watch_recursive -> watch_enabled
  so recording mechanism works when watch_recursive is false
- Build RefPathIndex from patch_apply data instead of redundant 4.8s
  WalkDir + 5,854 file re-reads (populate_from_dir)
- Use ServeSession::new_oneshot() for sourcemap without --watch
- Restore simple synchronous watch setup (implicit during reads)

Serve: >180s (never completed) -> ~8s to Listening
Sourcemap: 14.3s -> ~9s
All 489 tests passing.

CHANGELOG.md

@@ -31,6 +31,8 @@ Making a new release? Simply add the new header with the version and date undern
 
 ## Unreleased
 
+* Add .gitignore for logs and refactor ServeSession to include path_roots in init_tree return
+
 ## [8.5.6] (March 8th, 2026)
 
 * Add asynchronous log file compression with lowered thread priority to avoid impacting main workloads

Cargo.lock

@@ -1030,15 +1030,6 @@ version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "37909eebbb50d72f9059c3b6d82c0463f2ff062c9e95845c43a6c9c0355411be"
 
-[[package]]
-name = "file-id"
-version = "0.2.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e1fc6a637b6dc58414714eddd9170ff187ecb0933d4c7024d1abbd23a3cc26e9"
-dependencies = [
- "windows-sys 0.60.2",
-]
-
 [[package]]
 name = "filetime"
 version = "0.2.27"
@@ -1920,7 +1911,7 @@ dependencies = [
  "fs-err",
  "log",
  "notify",
- "notify-debouncer-full",
+ "notify-debouncer-mini",
  "serde",
  "tempfile",
 ]
@@ -1991,16 +1982,15 @@ dependencies = [
 ]
 
 [[package]]
-name = "notify-debouncer-full"
+name = "notify-debouncer-mini"
 version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c02b49179cfebc9932238d04d6079912d26de0379328872846118a0fa0dbb302"
+checksum = "17849edfaabd9a5fef1c606d99cfc615a8e99f7ac4366406d86c7942a3184cf2"
 dependencies = [
- "file-id",
  "log",
  "notify",
  "notify-types",
- "walkdir",
+ "tempfile",
 ]
 
 [[package]]

crates/memofs/Cargo.toml

@@ -18,14 +18,9 @@ homepage = "https://github.com/UserGeneratedLLC/rojo/tree/master/memofs"
 crossbeam-channel = "0.5.15"
 fs-err = "3"
 log = "0.4"
-notify-debouncer-full = "0.7"
-serde = { version = "1.0.228", features = ["derive"] }
-
-[target.'cfg(target_os = "macos")'.dependencies]
-notify = { version = "8.2", features = ["macos_kqueue"] }
-
-[target.'cfg(not(target_os = "macos"))'.dependencies]
 notify = "8.2"
+notify-debouncer-mini = "0.7"
+serde = { version = "1.0.228", features = ["derive"] }
 
 [dev-dependencies]
 tempfile = "3.26.0"

crates/memofs/src/lib.rs

@@ -190,7 +190,7 @@ impl VfsInner {
     fn read_raw(&mut self, path: &Path) -> io::Result<Vec<u8>> {
         if let Some(cache) = &mut self.prefetch_cache {
             if let Some(contents) = cache.files.remove(path) {
-                if self.watch_enabled && self.watch_recursive {
+                if self.watch_enabled {
                     self.watch_or_record(path)?;
                 }
                 return Ok(contents);
@@ -199,7 +199,7 @@ impl VfsInner {
 
         let contents = self.backend.read(path)?;
 
-        if self.watch_enabled && self.watch_recursive {
+        if self.watch_enabled {
             self.watch_or_record(path)?;
         }
 

crates/memofs/src/std_backend.rs

@@ -4,11 +4,7 @@ use std::{collections::HashSet, io};
 
 use crossbeam_channel::{Receiver, Sender};
 use notify::RecursiveMode;
-use notify_debouncer_full::{
+use notify_debouncer_mini::{new_debouncer, DebounceEventResult, DebouncedEventKind, Debouncer};
-    new_debouncer,
-    notify::event::{CreateKind, EventKind, ModifyKind, RemoveKind, RenameMode},
-    DebounceEventResult, Debouncer, RecommendedCache,
-};
 
 use crate::{DirEntry, Metadata, ReadDir, VfsBackend, VfsEvent};
 
@@ -55,7 +51,7 @@ pub type CriticalErrorHandler = Box<dyn Fn(WatcherCriticalError) -> bool + Send
 
 /// `VfsBackend` that uses `std::fs` and the `notify` crate.
 pub struct StdBackend {
-    debouncer: Debouncer<notify::RecommendedWatcher, RecommendedCache>,
+    debouncer: Debouncer<notify::RecommendedWatcher>,
     watcher_receiver: Receiver<VfsEvent>,
     watches: HashSet<PathBuf>,
     recursive_watches: HashSet<PathBuf>,
@@ -123,19 +119,25 @@ impl StdBackend {
         event_tx: Sender<VfsEvent>,
         error_tx: Sender<WatcherCriticalError>,
         error_handler: CriticalErrorHandler,
-    ) -> Debouncer<notify::RecommendedWatcher, RecommendedCache> {
+    ) -> Debouncer<notify::RecommendedWatcher> {
-        // Use 50ms debounce timeout (same as the old v4 implementation)
         let debounce_timeout = Duration::from_millis(50);
 
         new_debouncer(
             debounce_timeout,
-            None, // Use default tick rate
+            move |result: DebounceEventResult| match result {
-            move |result: DebounceEventResult| {
-                match result {
                 Ok(events) => {
                     for event in events {
-                            let vfs_events = Self::convert_event(&event.event);
+                        let vfs_event = match event.kind {
-                            for vfs_event in vfs_events {
+                            DebouncedEventKind::Any | DebouncedEventKind::AnyContinuous => {
+                                if event.path.exists() {
+                                    VfsEvent::Write(event.path)
+                                } else {
+                                    VfsEvent::Remove(event.path)
+                                }
+                            }
+                            _ => continue,
+                        };
+                        log::trace!("VFS debounced event: {:?}", &vfs_event);
                         if let Err(err) = event_tx.send(vfs_event) {
                             let critical_err =
                                 WatcherCriticalError::ChannelSendFailed(err.to_string());
@@ -146,113 +148,19 @@ impl StdBackend {
                         }
                     }
                 }
-                    }
+                Err(error) => {
-                    Err(errors) => {
-                        for error in errors {
-                            // Check if this is a rescan request
-                            if error.paths.is_empty() {
-                                let critical_err = WatcherCriticalError::RescanRequired;
-                                let _ = error_tx.send(critical_err.clone());
-                                if error_handler(critical_err) {
-                                    return;
-                                }
-                            } else {
                     let critical_err = WatcherCriticalError::WatcherError {
                         error: format!("{:?}", error.kind),
                         path: error.paths.first().cloned(),
                     };
                     let _ = error_tx.send(critical_err.clone());
-                                if error_handler(critical_err) {
+                    error_handler(critical_err);
-                                    return;
-                                }
-                            }
-                        }
-                    }
                 }
             },
         )
         .expect("Failed to create file watcher debouncer")
     }
 
-    /// Convert a notify event to our VfsEvent(s)
-    fn convert_event(event: &notify::Event) -> Vec<VfsEvent> {
-        let mut vfs_events = Vec::new();
-
-        match &event.kind {
-            // Create events
-            EventKind::Create(CreateKind::File)
-            | EventKind::Create(CreateKind::Folder)
-            | EventKind::Create(CreateKind::Any)
-            | EventKind::Create(CreateKind::Other) => {
-                for path in &event.paths {
-                    vfs_events.push(VfsEvent::Create(path.clone()));
-                }
-            }
-
-            // Modify events (treat as Write)
-            EventKind::Modify(ModifyKind::Data(_))
-            | EventKind::Modify(ModifyKind::Any)
-            | EventKind::Modify(ModifyKind::Other) => {
-                for path in &event.paths {
-                    vfs_events.push(VfsEvent::Write(path.clone()));
-                }
-            }
-
-            // Metadata changes - we don't care about these for Rojo's purposes
-            EventKind::Modify(ModifyKind::Metadata(_)) => {}
-
-            // Name changes (renames) - the debouncer-full handles rename tracking
-            EventKind::Modify(ModifyKind::Name(RenameMode::Both)) => {
-                // Both paths present: old path at [0], new path at [1]
-                if event.paths.len() >= 2 {
-                    vfs_events.push(VfsEvent::Remove(event.paths[0].clone()));
-                    vfs_events.push(VfsEvent::Create(event.paths[1].clone()));
-                }
-            }
-            EventKind::Modify(ModifyKind::Name(RenameMode::From)) => {
-                // Only the old path - treat as removal
-                for path in &event.paths {
-                    vfs_events.push(VfsEvent::Remove(path.clone()));
-                }
-            }
-            EventKind::Modify(ModifyKind::Name(RenameMode::To)) => {
-                // Only the new path - treat as creation
-                for path in &event.paths {
-                    vfs_events.push(VfsEvent::Create(path.clone()));
-                }
-            }
-            EventKind::Modify(ModifyKind::Name(RenameMode::Any))
-            | EventKind::Modify(ModifyKind::Name(RenameMode::Other)) => {
-                // Ambiguous rename - treat as modification
-                for path in &event.paths {
-                    vfs_events.push(VfsEvent::Write(path.clone()));
-                }
-            }
-
-            // Remove events
-            EventKind::Remove(RemoveKind::File)
-            | EventKind::Remove(RemoveKind::Folder)
-            | EventKind::Remove(RemoveKind::Any)
-            | EventKind::Remove(RemoveKind::Other) => {
-                for path in &event.paths {
-                    vfs_events.push(VfsEvent::Remove(path.clone()));
-                }
-            }
-
-            // Access events - we don't care about these
-            EventKind::Access(_) => {}
-
-            // Other/Any events - treat as potential modifications
-            EventKind::Other | EventKind::Any => {
-                for path in &event.paths {
-                    vfs_events.push(VfsEvent::Write(path.clone()));
-                }
-            }
-        }
-
-        vfs_events
-    }
-
     /// Returns a receiver for critical errors from the watcher thread.
     ///
     /// Poll this alongside `event_receiver()` to detect when watching becomes unreliable.
@@ -347,7 +255,7 @@ impl VfsBackend for StdBackend {
         } else {
             RecursiveMode::NonRecursive
         };
-        match self.debouncer.watch(path, mode) {
+        match self.debouncer.watcher().watch(path, mode) {
             Ok(()) => {
                 log::debug!(
                     "Watching path ({}): {}",
@@ -374,7 +282,7 @@ impl VfsBackend for StdBackend {
     fn unwatch(&mut self, path: &Path) -> io::Result<()> {
         let was_watched = self.watches.contains(path);
 
-        match self.debouncer.unwatch(path) {
+        match self.debouncer.watcher().unwatch(path) {
             Ok(()) => {
                 if was_watched {
                     log::info!("Unwatched path: {}", path.display());

src/cli/sourcemap.rs

@@ -79,7 +79,17 @@ impl SourcemapCommand {
         let vfs = Vfs::new_default();
         vfs.set_watch_enabled(self.watch);
 
-        let session = ServeSession::new(vfs, project_path, None)?;
+        let session_start = std::time::Instant::now();
+        let session = if self.watch {
+            ServeSession::new(vfs, project_path, None)?
+        } else {
+            ServeSession::new_oneshot(vfs, project_path)?
+        };
+        log::debug!(
+            "[PERF] ServeSession::new() total: {:.1?}",
+            session_start.elapsed()
+        );
+
         let mut cursor = session.message_queue().cursor();
 
         let filter = if self.include_non_scripts {
@@ -93,6 +103,7 @@ impl SourcemapCommand {
             .build_global()
             .ok();
 
+        let sm_start = std::time::Instant::now();
         write_sourcemap(
             &session,
             self.output.as_deref(),
@@ -100,6 +111,7 @@ impl SourcemapCommand {
             self.absolute,
             false,
         )?;
+        log::debug!("[PERF] write_sourcemap: {:.1?}", sm_start.elapsed());
 
         if self.watch {
             if !std::io::stdin().is_terminal() {
@@ -259,6 +271,7 @@ pub(crate) fn write_sourcemap(
     use_absolute_paths: bool,
     quiet: bool,
 ) -> anyhow::Result<()> {
+    let t0 = std::time::Instant::now();
     let tree = session.tree();
 
     let canonical_project_dir = session.root_dir().to_path_buf();
@@ -270,22 +283,32 @@ pub(crate) fn write_sourcemap(
         filter,
         use_absolute_paths,
     );
+    let t1 = std::time::Instant::now();
 
     if let Some(output_path) = output {
-        // Use standard JSON (not JSON5) for sourcemaps - required by external tools like LSPs
         let json_output = serde_json::to_string(&root_node)?;
+        let t2 = std::time::Instant::now();
 
-        // Use atomic write (temp file + rename) to prevent file watchers from
-        // reading partial files. Rename is atomic on all major filesystems when
-        // source and destination are on the same filesystem.
         write_atomic(output_path, json_output.as_bytes())?;
+        let t3 = std::time::Instant::now();
+
+        log::debug!(
+            "[PERF] write_sourcemap: tree_walk={:.1?}, json_serialize={:.1?} ({} bytes), write={:.1?}",
+            t1 - t0,
+            t2 - t1,
+            json_output.len(),
+            t3 - t2,
+        );
 
         if !quiet {
             println!("Created sourcemap at {}", output_path.display());
         }
     } else {
-        // Use standard JSON (not JSON5) for sourcemaps - required by external tools like LSPs
         let output = serde_json::to_string(&root_node)?;
+        log::debug!(
+            "[PERF] write_sourcemap: tree_walk={:.1?}, json_serialize=inline",
+            t1 - t0
+        );
         println!("{}", output);
     }
 

src/rojo_ref.rs

@@ -326,6 +326,22 @@ impl RefPathIndex {
         }
     }
 
+    /// Build from pre-collected entries (avoids re-walking the directory tree).
+    pub fn from_entries(entries: Vec<(String, PathBuf)>) -> Self {
+        let mut index = Self::new();
+        let count = entries.len();
+        for (ref_path, meta_file) in entries {
+            index.add(&ref_path, &meta_file);
+        }
+        if count > 0 {
+            log::debug!(
+                "RefPathIndex: built from {} collected Rojo_Ref_* entries",
+                count
+            );
+        }
+        index
+    }
+
     /// Record that `meta_file` contains a `Rojo_Ref_*` attribute with value
     /// `ref_path` (the instance path string, e.g., "Workspace/Model/Part1").
     pub fn add(&mut self, ref_path: &str, meta_file: &Path) {

src/serve_session.rs

@@ -326,12 +326,22 @@ pub fn collect_path_roots(node: &crate::project::ProjectNode, base: &Path, out:
 impl ServeSession {
     /// Shared initialization: loads the project and builds the initial
     /// snapshot tree. Used by both `new()` and `new_oneshot()`.
-    /// Returns the walked paths from prefetch (if available) for syncback reuse.
+    /// Returns the walked paths from prefetch (if available) for syncback reuse,
+    /// plus collected ref path index entries for building RefPathIndex.
+    #[allow(clippy::type_complexity)]
     fn init_tree(
         vfs: &Vfs,
         start_path: &Path,
-    ) -> Result<(Project, RojoTree, Option<HashSet<PathBuf>>, Vec<PathBuf>), ServeSessionError>
+    ) -> Result<
-    {
+        (
+            Project,
+            RojoTree,
+            Option<HashSet<PathBuf>>,
+            Vec<PathBuf>,
+            Vec<(String, std::path::PathBuf)>,
+        ),
+        ServeSessionError,
+    > {
         log::trace!("Starting new ServeSession at path {}", start_path.display());
 
         let root_project = Project::load_initial_project(vfs, start_path)?;
@@ -413,48 +423,27 @@ impl ServeSession {
 
         let snap_start = Instant::now();
         log::trace!("Generating snapshot of instances from VFS");
-        let was_watch_enabled = vfs.is_watch_enabled();
-        vfs.set_watch_enabled(false);
         let snapshot = snapshot_from_vfs(&instance_context, vfs, start_path)?;
-        vfs.set_watch_enabled(was_watch_enabled);
         log::debug!("Snapshot built in {:.1?}", snap_start.elapsed());
 
         vfs.clear_prefetch_cache();
 
         let patch_start = Instant::now();
-
-        if vfs.is_watch_enabled() {
-            std::thread::scope(|s| {
-                s.spawn(|| {
-                    let watch_start = Instant::now();
-                    let mut watch_count: usize = 0;
-                    for root in &path_roots {
-                        let _ = vfs.watch(root);
-                        watch_count += 1;
-                    }
-                    log::debug!(
-                        "Set up {} watches in {:.1?}",
-                        watch_count,
-                        watch_start.elapsed(),
-                    );
-                });
-
         log::trace!("Computing initial patch set");
         let patch_set = compute_patch_set(snapshot, &tree, root_id);
 
         log::trace!("Applying initial patch set");
-                apply_patch_set(&mut tree, patch_set);
+        let applied = apply_patch_set(&mut tree, patch_set);
-            });
+        let ref_path_entries = applied.ref_path_index_entries;
-        } else {
+        log::debug!("Patch computed + applied in {:.1?}", patch_start.elapsed());
-            log::trace!("Computing initial patch set");
-            let patch_set = compute_patch_set(snapshot, &tree, root_id);
 
-            log::trace!("Applying initial patch set");
+        Ok((
-            apply_patch_set(&mut tree, patch_set);
+            root_project,
-        }
+            tree,
-        log::debug!("Watch + patch in {:.1?}", patch_start.elapsed());
+            walked_paths,
-
+            path_roots,
-        Ok((root_project, tree, walked_paths, path_roots))
+            ref_path_entries,
+        ))
     }
 
     /// Start a new serve session from the given in-memory filesystem and start
@@ -471,7 +460,10 @@ impl ServeSession {
         let start_path = start_path.as_ref();
         let start_time = Instant::now();
 
-        let (root_project, tree, _walked_paths, _path_roots) = Self::init_tree(&vfs, start_path)?;
+        let t_init_start = Instant::now();
+        let (root_project, tree, _walked_paths, _path_roots, ref_path_entries) =
+            Self::init_tree(&vfs, start_path)?;
+        let t_init_tree = Instant::now();
 
         let session_id = SessionId::new();
         let message_queue = MessageQueue::new();
@@ -482,29 +474,26 @@ impl ServeSession {
 
         let (tree_mutation_sender, tree_mutation_receiver) = crossbeam_channel::unbounded();
         let suppressed_paths = Arc::new(Mutex::new(std::collections::HashMap::new()));
-        let ref_path_index = {
+        let ref_path_index = Arc::new(Mutex::new(crate::RefPathIndex::from_entries(
-            let mut index = crate::RefPathIndex::new();
+            ref_path_entries,
-            let tree_guard = tree.lock().unwrap();
+        )));
-            let mut ref_roots = Vec::new();
+        let t_ref_index = Instant::now();
-            collect_path_roots(
-                &root_project.tree,
-                root_project.folder_location(),
-                &mut ref_roots,
-            );
-            for root in &ref_roots {
-                index.populate_from_dir(root, &tree_guard);
-            }
-            drop(tree_guard);
-            Arc::new(Mutex::new(index))
-        };
 
         let git_repo_root = crate::git::git_repo_root(root_project.folder_location());
         let initial_head_commit = git_repo_root
             .as_deref()
             .and_then(crate::git::git_head_commit);
+        let t_git = Instant::now();
 
         let path_ignore_rules = root_project.path_ignore_rules();
 
+        log::debug!(
+            "[PERF] ServeSession::new breakdown: init_tree={:.1?}, ref_path_index={:.1?}, git={:.1?}",
+            t_init_tree - t_init_start,
+            t_ref_index - t_init_tree,
+            t_git - t_ref_index,
+        );
+
         log::trace!("Starting ChangeProcessor");
         let change_processor = ChangeProcessor::start(
             Arc::clone(&tree),
@@ -547,7 +536,8 @@ impl ServeSession {
         let start_path = start_path.as_ref();
         let start_time = Instant::now();
 
-        let (root_project, tree, walked_paths, _path_roots) = Self::init_tree(&vfs, start_path)?;
+        let (root_project, tree, walked_paths, _path_roots, _ref_entries) =
+            Self::init_tree(&vfs, start_path)?;
 
         Ok(Self {
             change_processor: None,

src/snapshot/patch.rs

@@ -1,6 +1,6 @@
 //! Defines the data structures used for describing instance patches.
 
-use std::collections::HashSet;
+use std::{collections::HashSet, path::PathBuf};
 
 use rbx_dom_weak::{
     types::{Ref, Variant},
@@ -81,6 +81,11 @@ pub struct AppliedPatchSet {
     pub removed: Vec<Ref>,
     pub added: Vec<Ref>,
     pub updated: Vec<AppliedPatchUpdate>,
+
+    /// Collected during patch application: `(resolved_absolute_ref_path, meta_or_model_file_path)`.
+    /// Used to build `RefPathIndex` without re-walking the directory tree.
+    #[serde(skip)]
+    pub ref_path_index_entries: Vec<(String, PathBuf)>,
 }
 
 impl AppliedPatchSet {
@@ -89,6 +94,7 @@ impl AppliedPatchSet {
             removed: Vec::new(),
             added: Vec::new(),
             updated: Vec::new(),
+            ref_path_index_entries: Vec::new(),
         }
     }
 

src/snapshot/patch_apply.rs

@@ -3,6 +3,8 @@
 use std::{
     collections::{HashMap, HashSet},
     mem::take,
+    path::PathBuf,
+    time::Instant,
 };
 
 use rbx_dom_weak::{
@@ -24,14 +26,20 @@ use crate::{
 /// tree in sync with Rojo's.
 #[profiling::function]
 pub fn apply_patch_set(tree: &mut RojoTree, patch_set: PatchSet) -> AppliedPatchSet {
+    let t0 = Instant::now();
     let mut context = PatchApplyContext::default();
 
+    let removal_count = patch_set.removed_instances.len();
+    let addition_count = patch_set.added_instances.len();
+    let update_count = patch_set.updated_instances.len();
+
     {
         profiling::scope!("removals");
         for removed_id in patch_set.removed_instances {
             apply_remove_instance(&mut context, tree, removed_id);
         }
     }
+    let t1 = Instant::now();
 
     {
         profiling::scope!("additions");
@@ -39,6 +47,7 @@ pub fn apply_patch_set(tree: &mut RojoTree, patch_set: PatchSet) -> AppliedPatch
             apply_add_child(&mut context, tree, add_patch.parent_id, add_patch.instance);
         }
     }
+    let t2 = Instant::now();
 
     {
         profiling::scope!("updates");
@@ -46,6 +55,22 @@ pub fn apply_patch_set(tree: &mut RojoTree, patch_set: PatchSet) -> AppliedPatch
             apply_update_child(&mut context, tree, update_patch);
         }
     }
+    let t3 = Instant::now();
+
+    log::debug!(
+        "[PERF] patch_apply phases: removals={} in {:.1?}, additions={} in {:.1?}, updates={} in {:.1?}",
+        removal_count, t1 - t0,
+        addition_count, t2 - t1,
+        update_count, t3 - t2,
+    );
+    log::debug!(
+        "[PERF] patch_apply context: snapshot_id_map={}, has_refs={}, attr_refs={}, path_refs={}, cleanup={}",
+        context.snapshot_id_to_instance_id.len(),
+        context.has_refs_to_rewrite.len(),
+        context.attribute_refs_to_rewrite.keys().count(),
+        context.path_refs_to_rewrite.keys().count(),
+        context.instances_needing_attr_cleanup.len(),
+    );
 
     finalize_patch_application(context, tree)
 }
@@ -90,6 +115,10 @@ struct PatchApplyContext {
     /// format and should not persist in the live game.
     instances_needing_attr_cleanup: HashSet<Ref>,
 
+    /// Collected `(resolved_absolute_ref_path, meta_or_model_file_path)` entries
+    /// for building `RefPathIndex` without a redundant directory walk.
+    ref_path_index_entries: Vec<(String, PathBuf)>,
+
     /// The current applied patch result, describing changes made to the tree.
     applied_patch_set: AppliedPatchSet,
 }
@@ -105,7 +134,12 @@ struct PatchApplyContext {
 /// where we build up a map of snapshot IDs to instance IDs as they're created,
 /// then apply properties all at once at the end.
 #[profiling::function]
-fn finalize_patch_application(context: PatchApplyContext, tree: &mut RojoTree) -> AppliedPatchSet {
+fn finalize_patch_application(
+    mut context: PatchApplyContext,
+    tree: &mut RojoTree,
+) -> AppliedPatchSet {
+    let finalize_start = Instant::now();
+
     for id in context.has_refs_to_rewrite {
         let mut instance = tree
             .get_instance_mut(id)
@@ -119,11 +153,13 @@ fn finalize_patch_application(context: PatchApplyContext, tree: &mut RojoTree) -
             }
         }
     }
+    let t_refs_rewrite = Instant::now();
 
     // IMPORTANT: Rojo_Target_* (legacy) must be resolved BEFORE Rojo_Ref_*
     // (path-based) so that path-based results overwrite legacy results when
     // both exist for the same property. Do not reorder these two blocks.
     let mut real_rewrites = Vec::new();
+    let attr_ref_count = context.attribute_refs_to_rewrite.keys().count();
     for (id, map) in context.attribute_refs_to_rewrite {
         for (prop_name, prop_value) in map {
             if let Some(target) = tree.get_specified_id(&RojoRef::new(prop_value)) {
@@ -135,11 +171,29 @@ fn finalize_patch_application(context: PatchApplyContext, tree: &mut RojoTree) -
             .expect("Invalid instance ID in deferred attribute ref map");
         instance.properties_mut().extend(real_rewrites.drain(..));
     }
+    let t_attr_refs = Instant::now();
 
     // Handle path-based references (Rojo_Ref_)
     let mut path_rewrites = Vec::new();
+    let _path_ref_count = context.path_refs_to_rewrite.keys().count();
+    let mut path_ref_total = 0usize;
+    let mut path_ref_resolved = 0usize;
+    let mut path_ref_failed = 0usize;
     for (id, map) in context.path_refs_to_rewrite {
+        let source_abs = crate::ref_target_path_from_tree(tree, id);
+        let meta_file = find_meta_or_model_path(tree, id);
+
         for (prop_name, path) in map {
+            path_ref_total += 1;
+
+            if let Some(meta_path) = &meta_file {
+                let resolved = crate::resolve_ref_path_to_absolute(&path, &source_abs)
+                    .unwrap_or_else(|| path.clone());
+                context
+                    .ref_path_index_entries
+                    .push((resolved, meta_path.clone()));
+            }
+
             if let Some(target) = tree.resolve_ref_path(&path, id) {
                 log::trace!(
                     "Resolved path reference {} -> {} (path: {})",
@@ -147,8 +201,10 @@ fn finalize_patch_application(context: PatchApplyContext, tree: &mut RojoTree) -
                     target,
                     path
                 );
+                path_ref_resolved += 1;
                 path_rewrites.push((prop_name, Variant::Ref(target)));
             } else {
+                path_ref_failed += 1;
                 log::debug!(
                     "Could not resolve path reference {} at path '{}' - instance not found in tree",
                     prop_name,
@@ -163,9 +219,11 @@ fn finalize_patch_application(context: PatchApplyContext, tree: &mut RojoTree) -
             instance.properties_mut().extend(path_rewrites.drain(..));
         }
     }
+    let t_path_refs = Instant::now();
 
     // Clean up Rojo ref attributes - they're only used for transport in the file
     // format and should not persist in the live game
+    let cleanup_count = context.instances_needing_attr_cleanup.len();
     for id in context.instances_needing_attr_cleanup {
         let mut instance = match tree.get_instance_mut(id) {
             Some(inst) => inst,
@@ -195,8 +253,25 @@ fn finalize_patch_application(context: PatchApplyContext, tree: &mut RojoTree) -
             attributes.remove(key);
         }
     }
+    let t_cleanup = Instant::now();
 
-    context.applied_patch_set
+    log::debug!(
+        "[PERF] finalize_patch_application: refs_rewrite={:.1?}, attr_refs({})={:.1?}, path_refs({}, ok={}, fail={})={:.1?}, cleanup({})={:.1?}, total={:.1?}",
+        t_refs_rewrite - finalize_start,
+        attr_ref_count,
+        t_attr_refs - t_refs_rewrite,
+        path_ref_total,
+        path_ref_resolved,
+        path_ref_failed,
+        t_path_refs - t_attr_refs,
+        cleanup_count,
+        t_cleanup - t_path_refs,
+        t_cleanup - finalize_start,
+    );
+
+    let mut result = context.applied_patch_set;
+    result.ref_path_index_entries = context.ref_path_index_entries;
+    result
 }
 
 fn apply_remove_instance(context: &mut PatchApplyContext, tree: &mut RojoTree, removed_id: Ref) {
@@ -319,6 +394,27 @@ fn apply_update_child(context: &mut PatchApplyContext, tree: &mut RojoTree, patc
     context.applied_patch_set.updated.push(applied_patch)
 }
 
+fn is_meta_or_model(name: &str) -> bool {
+    name.ends_with(".meta.json5")
+        || name.ends_with(".model.json5")
+        || name.ends_with(".meta.json")
+        || name.ends_with(".model.json")
+}
+
+fn find_meta_or_model_path(tree: &RojoTree, id: Ref) -> Option<PathBuf> {
+    let instance = tree.get_instance(id)?;
+    instance
+        .metadata()
+        .relevant_paths
+        .iter()
+        .find(|p| {
+            p.file_name()
+                .and_then(|n| n.to_str())
+                .is_some_and(is_meta_or_model)
+        })
+        .cloned()
+}
+
 /// Calculates manually-specified Ref properties and marks them in the provided
 /// `PatchApplyContext` to be rewritten at the end of the patch application
 /// process.